Lab-grown cartilage fixes damaged knees

Tissue engineering can effectively fix damaged knee cartilage, researchers have shown for the first time. Cartilage cells donated by patients were grown on scaffolds in the lab before being implanted back into their knees. More than a year later analysis showed the cartilage had matured successfully, even in patients with osteoarthritis.

Tissue engineering uses a mixture of biology, chemistry and materials science to grow tissues in the lab just like those in the body. Until recently, most research has taken place in the lab.

The new study from tissue engineers at Bristol University, UK, is the first to look in detail at what happens to tissues after they have been implanted in patients. The researchers took cartilage-producing cells from 23 patients with knee injuries and grew them on scaffolds made from hyaluronic acid - a compound that occurs naturally in cartilage.

After two weeks of growth, the cells and scaffold were inserted to fix tears of up to 11 square centimetres in the knee cartilage of the patients. An average of 16 months later the researchers examined the health of the engineered tissue.

Arthritis hope

"We found the cartilage matures well, even in patients with early osteoarthritis," lead researcher Anthony Hollander told New Scientist. Osteoarthritis, or degenerative arthritis, is a condition most common in the elderly, where cartilage slowly disappears from joints. "In these patients it seems to mature even better, suggesting it might be possible to treat patients with that condition, not just accident patients."

Hollander's team used two methods to study the maturation of the cartilage. The first involved injecting antibodies attached to a fluorescent dye into the cartilage. An imaging device was then used to count the number of proteins in the cartilage to which the antibodies bound.

The researchers also used an "amino acid analysis" technique to extract the joined amino acids that link cartilage proteins. These were separated to determine if they were the type found in mature or immature cartilage.

In both tests, in just under half the patients, the team found all the hallmarks of natural mature cartilage, showing the engineered tissue was thriving in these patients. "We're the first to formally show cartilage implanted into damaged patients matures," says Hollander.

"Textbook" research

Although the researchers did not carry out physical tests of the patient's mobility, these testing techniques have previously been shown to provide a good indicator of the cartilage's function, suggesting movement should be improved too. The reason why not all patients benefited from the engineered cartilage is not yet clear, although Hollander says giving the engineered tissue longer to settle in may help.

The new study is a "textbook example" of how tissue engineering should work, says Julian Chaudhuri, a tissue engineer working on cartilage at Bath University, UK. "Every step is in place from growing the tissue to implanting in patients, and it's been shown to work," he says. "It looks very exciting."

Studies in this area are among the most under-developed of the many jigsaw pieces in the relatively young field of tissue engineering, says Chaudhuri. "It's a very interdisciplinary area, but there's not yet a huge amount of clinical work going on," he says. "Studies like Hollander's are very important to close the loop and feed back into research in the lab."

Journal reference: Tissue Engineering (vol 12, p 7)

If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.